Hydrogen isn't an energy source, it's really a way of making electrically generated power more portable (you get the hydrogen by splitting water, into hydrogen and oxygen, then you get the power by recombining them so you end up with water vapour in the atmosphere).

And the electricity to split the water in the first place could come from anywhere, but preferably solar/wind/tide driven generators.

What with that and biomass there shouldn't be a real problem, in replacing the oil and other fossil fuels. If we didn't have oil money in the driving seat.

Nuclear fission is just crazy, because of the radioactive waste problem. Nuclear fusion we haven't got yet, outside of H-Bombs, and maybe we never will. Apart from that wonderful nuclear fusion facility we've got shining down on us every day, at a safe distance, our Sun.